Plans for Henman Hill-style ground passes to the Olympic Park during London 2012 could be scuppered in the second week of the Games due to overcrowding fears.

London 2012 organisers had hoped to sell Non-Event Tickets and allow purchasers to sample the atmosphere at the Olympic Park and watch events on a double-sided big screen that will be moored in one of the canals that crisscross the site.

But it is now feared that while it should still be feasible to sell tens of thousands of Park-only tickets during the first week of the Games, once the 74,000-capacity main stadium is in use for track and field there will not be room for more people on the Park.

It is assumed that ticket holders for morning or afternoon sessions will linger longer in the Park, particularly if plans for a Wimbledon-style ticket recycling scheme go ahead that would immediately make available tickets from those who leave early or fail to show.

The London Organising Committee of the Olympic and Paralympic Games will not be granted a licence for the Park until after a key batch of test events in late April and early May.

It is feared that given the number of venues in use during the second week the capacity of the Park will not safely stretch to more than a few hundred non-event tickets per day, defeating the object.

If the plans are scuppered, it would deal a blow to Locog's ambition to make the atmosphere within the Park one of the defining features of the Games. It has promised to avoid the antiseptic atmosphere of Beijing and make the Park a vibrant space.

A lack of park tickets during the most high-profile events could also further disappoint prospective purchasers who have yet to secure a ticket to the Games due to high demand.

A final batch of 1.2m tickets across all sports except synchronised swimming are due to go on sale in April. Around 20,000 purchasers who missed out in both the first and second rounds of sales will have an exclusive 24-hour window, before 1m more who failed to secure tickets in the first round are given a chance to apply.

In addition, there are more than 1m tickets left to the men's and women's football matches around the country.